Unfortunately, most of it seems to be opinion based, from people at the 'sharp end' (if you pardon the pun) who therefore see much more than average.

The first objective part in the report says:

According to the British Crime Survey (BCS), overall violent crime has decreased by 41% since a peak in 1995.

Knives are used in about 8% of violent incidents, according to the BCS, a level that has largely remained the same during the past decade.

Unfortunately, it then moves onto the usual subjective viewpoints.

The report then says:

Richard Garside, the director of the Centre of Crime and Justice Studies at Kings College London, said: "If you look at the figures for the last 10 years the number of knife victims has remained relatively stable - although there have been spikes - at 200 to 220 a year.

"But there is some evidence the demographic has changed. The average age of homicide victims overall has been going down, with younger and younger victims."

Other objective pieces of data look at changing demographics and geographical differences - unless I've missed something, the above seem to be the only objective data points regarding changes with time.